Which experimental physicist in The Big Bang Theory is played by Sara Gilbert?

The experimental physicist played by Sara Gilbert in The Big Bang Theory is Leslie Winkle.

Leslie Winkle, Ph.D., works in the same Caltech laboratory as Leonard Hofstadter and is presented as his scientific counterpart. Like Leonard, she is an experimental physicist, wears black-framed glasses, and usually appears in practical science-oriented clothing.

Leslie becomes one of Sheldon Cooper’s most persistent intellectual rivals. Their disagreements reflect the show’s contrast between competing scientific approaches, especially Leslie’s support for loop quantum gravity and Sheldon’s preference for string theory. Her sharp personality and willingness to challenge Sheldon make her an important early recurring character.

Sara Gilbert first appeared as Leslie in season 1, became part of the main cast in season 2, and later returned for guest appearances. Viewers sometimes confuse her with Stephanie Barnett, Emily Sweeney, or Priya Koothrappali, but those characters are associated with Leonard or Raj’s relationships rather than Gilbert’s role.